Here’s some great writing advice from Jane Espenson:
I promised you a half-ton of frozen fish. That’s a
half-ton of frozen fish.
we hear that, we know that the previous line was some kind of protest
about whether or not Shady Guy met his end of the bargain. We’ve
established the attitude of both characters by the end of line.
you look through your own writing, you may very well discover that
you’ve been doing this automatically, too. If not, try knocking off a
few opening lines, see if it doesn’t jump-start the scene!